Absorption heat pump and refrigeration systems are known for the mixing of solution depleted of refrigerant (weak liquor from the generator) with evaporated refrigerant (from the condenser frequently through a precooler). Exemplary systems are disclosed in U.S. Pat. Nos. 2,059,841 (Nov. 3, 1936 to Backstrom), 2,193,535 (Mar. 12, 1940 to Maiuri), 2,392,894 (Jan. 15, 1946 to Zwickl), 3,527,060 (Sept. 8, 1970 to Kruggel), 3,626,716 (Dec. 14, 1971 to Leonard, Jr.) and 3,638,452 (Feb. 1, 1972 to Kruggel). An older form of absorber is described on page 3 of U.S. Pat. No. 423,133 (Mar. 11, 1890 to Cooke). U.S. Pat. No. 3,638,452 discloses a coolant circuit through, sequentially, a low temperature portion of the absorber, the condenser and a high temperature portion of the absorber. U.S. Pat. No. 3,626,716 discloses an absorber with a liquid heat exchange medium circulated through an interior tube and an absorbent-refrigerant mixture circulated between the interior tube and an outer tube. U.S. Pat. No. 2,392,894 discloses an absorber with rich liquor (called strong aqua) pumped from the bottom of the absorber back through the upper portion of the absorber and cooling water circulated through the lower portion of the absorber.
The systems disclosed in the prior art, and particularly in U.S. Pat. No. 3,638,452, have the disadvantage that the evaporated refrigerant is introduced at or near the same end of the "absorber" as the weak liquor (or if one considers the "absorber heat exchanger" unit in U.S. Pat. No. 3,638,452 as a part of the absorber, then the refrigerant is introduced at an intermediate point). With such a design, at the point of refrigerant entry, the mixing of "dry" refrigerant (relatively free of absorbent vapor) with absorbent lowers the peak absorption temperature significantly. This lowering of the peak absorption temperature lowers the potential for using the absorption zone to heat coolant (for expulsion from the system in the cooling mode or for the heating load in the heating mode) or to preheat rich liquor.
The absorber units of the prior art also provide insufficient heat exchange and mass transfer surfaces to allow the vapor to reach a composition that approaches equibrium with the adjacent liquid. The advantages of the present invention are realized with absorption pairs such as R21-ETFE (discussed below); however, the advantages of the present invention can be realized as well with conventional absorption pairs such as ammonia-water or the many other absorption pairs known (see W. R. Hainsworth, "Refrigerants and Absorbents," Refrigerating Engineer Vol. 28, Nos. 3 and 4, August and September 1944 and U.S. Pat. No. 4,005,584, Feb. 1, 1977 to Li) and to be discovered.